This invention relates to a novel method of operating X-ray tubes, and a novel power supply for carrying out the method.
A major problem in roentgenography is radiation output variation especially in instruments that take their power from the conventional 115 or 230 volt line from a central power station. The voltage at a local outlet on the conventional line often varies substantially from its nominal value such as, for example, responsively to changes in the load placed on the line at other local outlets. Unless some sort of regulation is provided, the radiation output of an X-ray tube energized from the conventional line varies to an intolerable degree from its radiation output when the line voltage is at its nominal value.
Relatively high voltages, ranging upwardly from fifty kilovolts, are used for energizing X-ray tubes, and, for reasons of cost, it is not always desirable to provide regulated DC power supplies. Instead, an alternating voltage is usually applied between the cathode and the plate through a high voltage transformer, the primary winding of which is connected to the conventional power line through some sort of energizing circuitry. The output of the high voltage transformer is sometimes fed through a full wave rectifier, but often without filtering and without high voltage regulation.